Xee3 - A better Mac OS X's Preview.app
WinDirStat - WinDirStat is a disk usage statistics viewer and cleanup tool, inspired by KDirStat.
MacFly Pro - Smart assistant for better Mac performance
TreeSize - TreeSize tells you where precious disk space has gone to.
Power Mode Switcher for macOS - macOS Monterey introduced a new feature for some Macs called Low Power Mode so you can save energy while keeping your Mac cool and quiet.
SpaceSniffer - SpaceSniffer is a freeWare (donations are welcome) and portable tool application that lets you understand how folders and files are structured on your disks.